J/A+A/629/A111 L 98-59 (TOI 175) HARPS observations (Cloutier+, 2019)
Characterization of the L 98-59 multi-planetary system with HARPS:
Mass characterization of a hot super-Earth, a sub-Neptune, and a mass upper
limit on the third planet.
Cloutier R., Astudillo-Defru N., Bonfils X., Jenkins J.S., Berdinas Z.,
Ricker G., Vanderspek R., Latham D.W., Seager S., Winn J., Jenkins J.M.,
Almenara J.M., Bouchy F., Delfosse X., Diaz M.R., Diaz R.F., Doyon R.,
Figueira P., Forveille T., Kurtovic N.T., Lovis C., Mayor M., Menou K.,
Morgan E., Morris R., Muirhead P., Murgas F., Pepe F., Santos N.C.,
Segransan D., Smith J.C., Tenenbaum P., Torres G., Udry S., Vezie M.,
Vilasenor J.
<Astron. Astrophys. 629, A111 (2019)>
=2019A&A...629A.111C 2019A&A...629A.111C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Stars, double and multiple ; Exoplanets ;
Radial velocities
Keywords: stars: individual: L 98-59 - planetary systems - stars: low-mass -
planets and satellites: terrestrial planets -
techniques: radial velocities
Abstract:
L 98-59 (TIC 307210830, TOI-175) is a nearby M3 dwarf around which
TESS revealed three small transiting planets (0.80, 1.35, 1.57 Earth
radii) in a compact configuration with orbital periods shorter than
7.5 days. Here we aim to measure the masses of the known transiting
planets in this system using precise radial velocity (RV) measurements
taken with the HARPS spectrograph. We considered both trained and
untrained Gaussian process regression models of stellar activity,
which are modeled simultaneously with the planetary signals. Our RV
analysis was then supplemented with dynamical simulations to provide
strong constraints on the planets' orbital eccentricities by requiring
long-term stability. We measure the planet masses of the two outermost
planets to be 2.42±0.35 and 2.31±0.46 Earth masses, which confirms
the bulk terrestrial composition of the former and eludes to a
significant radius fraction in an extended gaseous envelope for the
latter. We are able to place an upper limit on the mass of the
smallest, innermost planet of <1.01 Earth masses with 95% confidence.
Our RV plus dynamical stability analysis places strong constraints on
the orbital eccentricities and reveals that each planet's orbit likely
has e<0.1. L 98-59 is likely a compact system of two rocky planets
plus a third outer planet with a lower bulk density possibly
indicative of the planet having retained a modest atmosphere. The
system offers a unique laboratory for studies of planet formation,
dynamical stability, and comparative atmospheric planetology as the
two outer planets are attractive targets for atmospheric
characterization through transmission spectroscopy. Continued RV
monitoring will help refine the characterization of the innermost
planet and potentially reveal additional planets in the system at
wider separations.
Description:
HARPS spectroscopic time-series of L 98-59 including radial velocities
and spectroscopic activity indices.
Objects:
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RA (ICRS) DE Designation(s)
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08 18 07.62 -68 18 46.8 L 98-59 = TOI 175
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
harps.dat 89 165 HARPS time-series
t175samp.dat 206 10000 MCMC posterior samples
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Byte-by-byte Description of file: harps.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d Time Timestamp (BJD-2457000)
13- 19 F7.1 m/s RV Radial velocity
21- 23 F3.1 m/s e_RV Radial velocity uncertainty
25- 28 F4.2 10-2 Halpha H-alpha index multiplied by 100
30- 33 F4.2 10-2 e_Halpha H-alpha index uncertainty
35- 38 F4.2 10-2 Hbeta H-beta index multiplied by 100
40- 43 F4.2 10-2 e_Hbeta H-beta index uncertainty
45- 49 F5.2 10-2 Hgamma H-gamma index multiplied by 100
51- 54 F4.2 10-2 e_Hgamma H-gamma index uncertainty
56- 59 F4.2 --- NaD Sodium doublet index
61- 64 F4.2 --- e_NaD Sodium doublet index uncertainty
66- 69 F4.2 --- Sindex S-index
71- 74 F4.2 --- e_Sindex S-index uncertainty
76- 81 F6.4 --- FWHM ? Full width at half maximum of the
cross-correlation function
83- 89 F7.4 --- BIS ? Bisector of the cross-correlation function
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Byte-by-byte Description of file: t175samp.dat
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Bytes Format Units Label Explanations
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1- 8 F8.6 m/s lna GP covariance amplitude
10- 18 F9.6 d lnlambda GP expontential timescale
20- 28 F9.6 --- lnGamma GP coherence
30- 37 F8.6 d lnPGP GP periodic timescale
39- 46 F8.6 m/s s RV jitter
48- 56 F9.6 m/s gamma0 Systemic velocity
58- 65 F8.6 d Pb L 98-59b orbital period
67- 77 F11.6 d T0b L 98-59b mid-transit time ((BJD-2457000)
79- 86 F8.6 m/s Kb L 98-59b semi-amplitude
88- 96 F9.6 --- hb L 98-59b h = sqrt(ecc)*cos(omega)
98-106 F9.6 --- kb L 98-59b k = sqrt(ecc)*sin(omega)
108-115 F8.6 d Pc L 98-59c orbital period
117-127 F11.6 d T0c L 98-59c mid-transit time (BJD-2457000)
129-136 F8.6 m/s Kc L 98-59c semi-amplitude
138-146 F9.6 --- hc L 98-59c h = sqrt(ecc)*cos(omega)
148-156 F9.6 --- kc L 98-59c k = sqrt(ecc)*sin(omega)
158-165 F8.6 d Pd L 98-59d orbital period
167-177 F11.6 d T0d L 98-59d mid-transit time (BJD-2457000)
179-186 F8.6 m/s Kd L 98-59d semi-amplitude
188-196 F9.6 --- hd L 98-59d h = sqrt(ecc)*cos(omega)
198-206 F9.6 --- kd L 98-59d k = sqrt(ecc)*sin(omega)
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Acknowledgements:
Ryan Cloutier, cloutier(at)astro.utoronto.ca
(End) Ryan Cloutier [Toronto], Patricia Vannier [CDS] 02-Sep-2019